title: Overtraining is associated with DNA damage in blood and skeletal muscle cells of Swiss mice.
abstract: BACKGROUND
  The alkaline version of the single-cell gel (comet) assay is a useful method for quantifying DNA damage. Although some studies on chronic and acute effects of exercise on DNA damage measured by the comet assay have been performed, it is unknown if an aerobic training protocol with intensity, volume, and load clearly defined will improve performance without leading to peripheral blood cell DNA damage. In addition, the effects of overtraining on DNA damage are unknown. Therefore, this study aimed to examine the effects of aerobic training and overtraining on DNA damage in peripheral blood and skeletal muscle cells in Swiss mice. To examine possible changes in these parameters with oxidative stress, we measured reduced glutathione (GSH) levels in total blood, and GSH levels and lipid peroxidation in muscle samples.
  
  
  RESULTS
  Performance evaluations (i.e., incremental load and exhaustive tests) showed significant intra and inter-group differences. The overtrained (OTR) group showed a significant increase in the percentage of DNA in the tail compared with the control (C) and trained (TR) groups. GSH levels were significantly lower in the OTR group than in the C and TR groups. The OTR group had significantly higher lipid peroxidation levels compared with the C and TR groups.
  
  
  CONCLUSIONS
  Aerobic and anaerobic performance parameters can be improved in training at maximal lactate steady state during 8 weeks without leading to DNA damage in peripheral blood and skeletal muscle cells or to oxidative stress in skeletal muscle cells. However, overtraining induced by downhill running training sessions is associated with DNA damage in peripheral blood and skeletal muscle cells, and with oxidative stress in skeletal muscle cells and total blood.
authors.affiliation: Universidade de São Paulo (USP), Escola de Educação Física e Esporte de Ribeirão Preto (EEFERP), Ribeirão Preto, São Paulo, Brasil. adelinosanchez@usp.br.
authors.forename: Bruno Cesar
authors.initials: BC
authors.lastname: Pereira
authors.forename: José Rodrigo
authors.initials: JR
authors.lastname: Pauli
authors.forename: Lusânia Maria Greggi
authors.initials: LM
authors.lastname: Antunes
authors.forename: Ellen Cristini
authors.initials: EC
authors.lastname: de Freitas
authors.forename: Mara Ribeiro
authors.initials: MR
authors.lastname: de Almeida
authors.forename: Vinícius
authors.initials: V
authors.lastname: de Paula Venâncio
authors.forename: Eduardo Rochete
authors.initials: ER
authors.lastname: Ropelle
authors.forename: Claudio Teodoro
authors.initials: CT
authors.lastname: de Souza
authors.forename: Dennys Esper
authors.initials: DE
authors.lastname: Cintra
authors.forename: Marcelo
authors.initials: M
authors.lastname: Papoti
authors.forename: Adelino Sanchez Ramos
authors.initials: AS
authors.lastname: da Silva
mesh_terms: D000818:Animals; D001773:Blood Cells / Q000378:metabolism*; D004249:DNA Damage; D005978:Glutathione / Q000737:chemistry; D008297:Male; D051379:Mice; D018482:Muscle, Skeletal / Q000378:metabolism*; D018384:Oxidative Stress; D010805:Physical Conditioning, Animal / Q000009:adverse effects*; D017392:Thiobarbituric Acid Reactive Substances / Q000737:chemistry
chemical_list: D017392:Thiobarbituric Acid Reactive Substances; D005978:Glutathione